1. Field of the Invention
The present invention relates to an improvement of a process for pyrolysis of dioxins by allowing a carbonaceous adsorbent such as activated carbon, activated cokes, etc. to adsorb dioxins, followed by treatment of the dioxins-adsorbed carbonaceous adsorbent at a high temperature (about 1300.degree. C.), such as combustion, etc. More particularly, the present invention relates to a process for pyrolysis of dioxins at a lower temperature. The term "dioxins" herein used is an abbreviation for polychlorodibenzodioxin and polychlorodibenzofuran, both of which belong to organochlorine compounds.
2. Related Art
Processes for pyrolysis of dioxins or dioxins-collected materials by exposing them to a high temperature are well known, but have such disadvantages as large energy consumption due to the pyrolysis at a very high temperature, e.g. about 1,300.degree. C., and inevitable waste of resources due to combustion loss of dioxin collectors, i.e. carbonaceous adsorbent. Furthermore, there are undesirable chances of recombination of the once decomposed dioxins into the original dioxins at the last stage of combustion. Thus, further improvements of the methods are still in demand.
For one of such improvements, the present inventor disclosed a process for low temperature pyrolysis in JP-A 5(1933)-301022, as will be hereinafter referred to under the caption "Disclosed Prior Art", where dioxins are thermally decomposed in an oxygen-deficient state, i.e. at an oxygen concentration of not more than 1% at a temperature of at least 350.degree. C. for at least one hour.